arXiv subjects

Marko Šimić

Publications and source records attributed to Marko Šimić.

6 recordsLinked to original sources

arXiv2026

Inverse Design of Integrated Photonic Components for Visible-Light Applications

Photonic integrated circuits (PICs) operating in the visible spectral range are crucial for quantum technologies, optical sensing, and nonlinear optics applications. However, their development is hampered by limited integration density and operational bandwidth, linked to low refractive index contrast and restricted parameter space in intuition-based PIC design. We address these bottlenecks with an adjoint-based, fabrication-aware inverse design workflow tailored for visible-spectrum photonics. By expanding the capabilities of FDTDX, an open-source, GPU-accelerated FDTD solver, we provide a versatile memory and runtime efficient inverse design platform. Demonstrating this approach on a silicon nitride (Si3N4) platform, we design, fabricate, and experimentally validate ultra-compact, broadband components for light routing, multiplexing, and polarization control. This work provides a scalable framework for high-density, high-performance visible-light PICs.

physics.optics↗

arXiv2026

Polarization vector conjugation in a photonic integrated circuit

We show how to perform polarization conjugation of light in a simple apparatus without any nonlinear optical materials, based on self-configuring Mach-Zehnder interferometers fed by a polarization splitter. This allows us to completely and automatically remove the polarization variations on a single beam or mode propagating through an optical system with arbitrary birefringence, such as a conventional optical fiber, and compensate polarization variations experienced in the forward direction by propagating the conjugated beam back through the system and recreating the original polarization at the source. We demonstrate this polarization conjugation in an optical fiber setup in different orientations with a measured polarization extinction ratio of -30 dB for the returned beam.

physics.optics↗

arXiv2026

Separating partially coherent light

Recent advances in optical imaging and communication increasingly involve high-dimensional, partially coherent light, creating a growing need for scalable tools to measure and manipulate coherence. Here, we demonstrate the automatic separation of spatially partially coherent light into "coherence modes" -- its orthogonal and mutually incoherent components. To make this separation possible, we exploit variational processing in layered self-configuring interferometer architectures in a silicon photonic circuit. This process formally finds and measures the eigenvectors and eigenvalues of the coherency matrix, hence measuring the partially coherent state, while leaving it intact and separated after optimization. Furthermore, we show that mutually incoherent beams, if spatially orthogonal, can be automatically separated even if they are completely overlapped, hence separating unknown laser beams based only on their mutual incoherence. Our experiment finds and separates the two strongest coherence modes starting from a nine-mode sampling of the partially or fully overlapping fields from two independent lasers. The method requires a number of physical components that scales linearly with the rank $r$ of the coherency matrix and operates through a sequence of $r$ in situ gradient-based optimizations enabled by electronic drive frequency multiplexing of interferometer phase shifters. We benchmark its performance against a mixture-based tomographic method, also implemented on chip. These results establish a scalable framework for programmable coherence analysis and control in imaging, communication, and photonic information processing.

physics.optics↗

arXiv2023

Optofluidic Force Induction as a Process Analytical Technology

Manufacturers of nanoparticle-based products rely on detailed information about critical process parameters, such as particle size and size distributions, concentration, and material composition, which directly reflect the quality of the final product. These process parameters are often obtained using offline characterization techniques that cannot provide the temporal resolution to detect dynamic changes in particle ensembles during a production process. To overcome this deficiency, we have recently introduced Optofluidic Force Induction (OF2i) for optical real-time counting with single particle sensitivity and high throughput. In this paper, we apply OF2i to highly polydisperse and multi modal particle systems, where we also monitor evolutionary processes over large time scales. For oil-in-water emulsions we detect in real time the transition between high-pressure homogenization states. For silicon carbide nanoparticles, we exploit the dynamic OF2i measurement capabilities to introduce a novel process feedback parameter based on the dissociation of particle agglomerates. Our results demonstrate that OF2i provides a versatile workbench for process feedback in a wide range of applications.

physics.app-ph↗

arXiv2023

Theoretical description of optofluidic force induction

Optofluidic force induction (OF2i) is an optical nanoparticle characterization scheme which achieves real-time optical counting with single-particle sensitivity and high throughput. In a recent paper [Šimić et al., Phys. Rev. Appl. 18, 024056 (2022)], we have demonstrated the working principle for standardized polystrene nanoparticles, and have developed a theoretical model to analyze the experimental data. In this paper we give a detailed account of the model ingredients including the full working equations, provide additional justification for the assumptions underlying OF2i, and discuss directions for further developments and future research.

physics.optics↗

arXiv2022

Real-time nanoparticle characterization through opto-fluidic force induction

We propose and demonstrate a novel scheme for optical nanoparticle characterization, optofluidic force induction (OF2i), which achieves real-time optical counting with single-particle sensitivity, high throughput, and for particle sizes ranging from tens of nanometers to several $μ$m. The particles to be analyzed flow through a microfluidic channel alongside a weakly focused laser vortex beam, which accomplishes 2D trapping of the particles in the transverse directions and size-dependent velocity changes due to the optical forces in the longitudinal direction. Upon monitoring the trajectories and velocity changes of each individually tracked particle, we obtain detailed information about the number based particle size distribution. A parameter-free model based on Maxwell's equations and Mie theory is shown to provide very good agreement with the experimental results for standardized particles of spherical shape. Our results prove that OF2i can provide a flexible work bench for numerous pharmaceutical and technological applications, as well as for medical diagnostics.

physics.optics↗